264 Scientific Intelligence. 
The product resulting from the multiplication of the number of units 
of weight and measures of height, or, as it is called, the product of mass 
and height, as well as the product of the mass and the square of its 
velocity, are called “vis viva of motion,” “ mechanical effect,” “dynam- 
ical effect,” “work done,” “ quantité de travail,” &e. 
The amount of mechanical work necessary for the heating of 1 kilo- 
m of water 1° C. has been determined by experiment to be 367 Km; 
therefore Km==0-00273 units of heat.’ 
¢ metres, the corresponding development of heat will be expressed 
the formula 000139° Xc?, 
Ill On the Measure of the Sun’s Heat,—The actinometer is an instru- 
ment invented by Sir John Herschel for the purpose of measuring the 
heating effect produced by the sun’s rays. It is essentially a thermome- 
ter with a large cylindrical bulb filled with a blue liquid, which 1s 
acted upon by the sun’s rays, and the expansion of which is measured 
by a graduated scale. 
rom observations made with this instrument, Sir John Herschel cal- 
culates the amount of heat received from the sun to be sufficient to 
In order to obtain smaller numbers, we shall call the quantity of heat 
necessary to raise a cubic mile of water 1° C. in temperature, 4 cubic 
mile of heat. Since one cubic mile of water weighs 408°54 billions of 
kilograms, a cubic mile of heat contains 408°54 billions of units of 
* How this important result is obtained bas been explained in my paper “ Die 
le finds it =772 foo SS LEC 7 as 
geographical mile =7420 metres, and one English mile =1608 metres. 
